EP0403002A1 - Verfahren zur elektrostatischen Pulverbeschichtung eines Gegenstandes mit pulverförmigen oder körnigen Partikeln und Vorrichtung zur Durchführung dieses Verfahrens - Google Patents

Verfahren zur elektrostatischen Pulverbeschichtung eines Gegenstandes mit pulverförmigen oder körnigen Partikeln und Vorrichtung zur Durchführung dieses Verfahrens Download PDF

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Publication number
EP0403002A1
EP0403002A1 EP90201486A EP90201486A EP0403002A1 EP 0403002 A1 EP0403002 A1 EP 0403002A1 EP 90201486 A EP90201486 A EP 90201486A EP 90201486 A EP90201486 A EP 90201486A EP 0403002 A1 EP0403002 A1 EP 0403002A1
Authority
EP
European Patent Office
Prior art keywords
particles
fluid
electrostatic field
support
jet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP90201486A
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English (en)
French (fr)
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EP0403002B1 (de
Inventor
Jean-Luc Houssaye
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tremplin SA
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Tremplin SA
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Publication date
Application filed by Tremplin SA filed Critical Tremplin SA
Priority to AT90201486T priority Critical patent/ATE99996T1/de
Publication of EP0403002A1 publication Critical patent/EP0403002A1/de
Application granted granted Critical
Publication of EP0403002B1 publication Critical patent/EP0403002B1/de
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
    • B05D1/22—Processes for applying liquids or other fluent materials performed by dipping using fluidised-bed technique
    • B05D1/24—Applying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C19/00—Apparatus specially adapted for applying particulate materials to surfaces
    • B05C19/02—Apparatus specially adapted for applying particulate materials to surfaces using fluidised-bed techniques
    • B05C19/025—Combined with electrostatic means

Definitions

  • the subject of the present invention is a process for electrostatic powdering intended to coat an object with powdery or granular particles, of the type consisting in directing these particles by means of an electrostatic field, towards a receiving element constituted by the object to be coated.
  • This invention extends to a device for implementing this method.
  • the coating of objects by electrostatic powdering is a process which has experienced a great boom in recent years, especially in industrial painting. This development is due to the advantages of this process, in particular as regards the improvement in the finish provided and the reduction in cost prices achieved compared with known coating processes.
  • the technique consists in placing a homogeneous layer of pulverulent material on an insulating support placed opposite the object to be coated, in fluidizing the particles either mechanically or electrically, in particular by means of a pulsating field, so as to obtain a uniform swirling and intense, and to create an electrostatic field between the support and the object so that the particles follow the lines of force of this field and come to deposit on the receiving object.
  • Such techniques in particular described in patents FR 2,146,886, FR 2,263,825 and DE 2,036,279, are very reliable when the receiving object is strictly made up of flat surfaces.
  • the present invention aims to overcome this drawback and aims to provide an improved electrostatic powdering process for coating uniformly objects of any shape with non-planar surfaces.
  • the invention relates to an electrostatic powdering process intended to coat with powdery or granular particles an object having portions of flat surfaces and portions of non-planar surfaces, said process consisting in placing a layer of particles on an insulating support. placed next to the object, to fluidize this layer of particles and to create an electrostatic field between the support and the object.
  • this process is characterized in that: the particles are subjected to the action of an electrostatic field generating lines of force driving said particles adapted to direct them towards the flat surfaces of the object, - And the trajectory of the particles is modified by means of at least one jet of fluid oriented so as to direct said particles towards the non-planar surfaces of the object.
  • the invention therefore consists in combining the action of an electrostatic field whose lines of force direct the particles towards the planar surfaces of the object, with a jet of fluid making it possible to deflect these particles from their trajectory and thus to direct them towards the non-planar surface portions of the object
  • This combination therefore makes it possible to uniformly sweep the surface to be treated and to deposit a uniform layer of coating on this surface.
  • the direction of the fluid jet relative to the surface to be covered can also be modified within a wide inclination range according to the shape and the dimensions of this surface, thus allowing the treatment of objects of very different shapes.
  • the particles are first subjected to the action of the electrostatic field, for a period of time suitable for uniformly coating the flat surfaces of the object, - secondly, the jet of fluid, while maintaining the electrostatic field in action, so as to deflect the particles towards the non-planar surfaces and uniformly coat the latter, - And the action of the electrostatic field and the jet of fluid is interrupted.
  • the particles are preferably subjected to the action of the electrostatic field for a period of time substantially comprised between 5 and 10 seconds, then to the combined action of the field and the jet of fluid for a period of time comprised substantially between 1 and 5 seconds.
  • the fluid used is preferably compressed air at a pressure substantially between 4 and 7 bars, which is delivered with a flow rate substantially between 0.1 and 0, 6 m3 / min, and at a distance substantially between 10 and 20 centimeters from the object.
  • the invention extends to an electrostatic powdering device for application to an object comprising portions of flat surfaces and portions of non-planar surfaces, of a coating of powdery or granular particles, of the type comprising an insulating support for particles, means adapted to fluidize the particles arranged on the support, and means generating an electrostatic field adapted to accelerate the fluidized particles and transport them to the object according to predetermined trajectories.
  • This device is characterized in that it comprises means for supplying a fluid provided with at least one fluid outlet disposed between the object and the support, near said support, and adapted to deliver said fluid according to a direction where it changes the trajectories of the particles.
  • the device shown in Figures 1 to 3 is an electrostatic powdering device suitable for covering objects with powdery particles.
  • This device is more particularly intended for an application of powder paint on one side of a "pedestal table".
  • Bo pedestal table we mean an object whose surface to be treated is a circular planar surface provided on its periphery with a concave groove delimited, on the one hand, by this planar surface and, on the other hand, by a cylindrical return perpendicular to said surface).
  • This device comprises, firstly, two cylindrical boxes made of a plastic material such as PVC, nested one inside the other: an internal box 2 of diameter corresponding to that of the mold of the mold, and an external box 1, intended to isolate the inner box 2 and of dimensions adapted to provide an interstitial space between the peripheral and bottom walls of said boxes. Shims 3 are also arranged in this interstitial space in order to ensure the positioning and the maintenance of the inner box 2 in the outer box 1.
  • the device also comprises two networks of electrodes disposed respectively inside the interior box 2 and in the interstitial space separating the bottom walls of the interior 2 and exterior 1 boxes.
  • the first network placed in the bottom of the inner box 2, consists of an assembly of compression springs 4 wound in the form of a spiral so that the distance between two turns is of the order of 3, 2 inches.
  • These springs 4 are carried by wires 5, arranged radially in the bottom of the inner box 2 and the ends of which are fixed to a metal ring 6 resting on the bottom wall of this box. These wires 5 and this ring 6 are furthermore arranged so as to maintain the springs 4 at approximately 1 cm above this bottom wall.
  • the second network of electrodes is made up of ten copper blades 7 30 millimeters wide welded to each other so as to form an orthogonal mesh. These blades 7 are covered with an aluminum foil intended to obtain a good distribution of the electrostatic charges and are fixed under the bottom wall of the inner box 2.
  • one of the ends of the spiral of springs 4 and one of the copper blades 7 are connected to a voltage source (not shown) so as to form an electrostatic vibrator of the type known per se, described in particular in French patents n ° 2.263.825 and 2.146.886.
  • the device also includes a compressed air supply system.
  • This system consists, first of all, of a cylindrical stitching angle fitting 8 disposed on the bottom wall of the inner box 2, in the center of the latter. On the inlet of this angle-fitting 8 is connected a pipe 9 for supplying compressed air with an internal diameter of 4 mm.
  • This pipe 9 is introduced into the inner box 2 through two openings arranged opposite in the peripheral walls of this inner box and the outer box 1, and is arranged so as to extend radially on the bottom wall of said inner box. Its external end is connected upstream to a tapping pipe (not shown) of compressed air delivered by a supply network.
  • This tapping pipe has an internal diameter of 10 millimeters greater than that of pipe 9, with a view to overcoming any fluctuations in the flow of compressed air.
  • the compressed air supply system finally comprises a plastic tip 10 mounted on the vertical outlet branch of the angle fitting 9.
  • This tip 10, of the same internal diameter as that of the angle fitting 9, has besides a length adapted so that the compressed air outlet is at a distance of between 0.5 cm and 10 cm from the bottom wall of the inner box 2.
  • the device finally comprises a mask arranged on the double box and intended to prevent the deposition of pulverulent material over a height of 20 centimeters from the surface of the return of the pedestal table.
  • this mask consists of a crown 11 of the same diameter as that of the matrix 13 of the mold, adapted to come to press internally against the return of this matrix.
  • This crown 11 made of plastic material reinforced with 30% glass fibers, is screwed onto a plywood support 12, itself secured to the outer box 1.
  • the distance between the surface to be treated and the network of springs 4 is of the order of 235 mm.
  • Such a device is adapted to be associated, in a conventional manner, with a support assembly managed by a programmable auto mat and adapted to automatically adjust this device in the mold.
  • the sequences for moving such a support are as follows: - horizontal linear movement in advance from a parking position to a position where the device is directly above the mold, - linear upward movement to the position where the mask is inserted in the mold, - linear downward movement of mask disengagement, - horizontal linear movement back to the parking position.
  • the programmable controller is also conventionally adapted to manage the operation of the electrostatic vibrator and the compressed air supply system, according to the process described below.
  • the bottom wall of the inner box 2 is uniformly covered with powder over a thickness suitable for this powder to be flush with the bottom of the springs 4 as much as possible. Furthermore, the matrix 13 of the mold is connected to the ground.
  • the powder transfer process takes place in two stages.
  • the powder is subjected to the electrostatic powdering system.
  • the powder layer resting on the bottom wall of the inner box 2 is fluidized by applying an alternating voltage between the two networks of electrodes 4 and 7 which then form an electrostatic vibrator. This vibrator continuously reverses the polarity of the powder which is thus charged.
  • the bottom of the inner box 2 is also subject to reverse polarity.
  • the network of electrodes 4 is placed under adjustable high voltage, of a value of 48 KV and between this network and the matrix 13 of the mold, grounded, forms an electrostatic field.
  • the charged particles follow the lines of force of this electrostatic field and are deposited on the flat surfaces of the matrix 13.
  • the groove of this matrix 13 receives very little powder during this operation.
  • the second step therefore consists in transferring the powder still charged, the electrodes being kept under tension, on the non-planar surfaces of the matrix 13, that is to say in the groove of the latter.
  • This result is obtained by actuating the compressed air supply system adapted to deliver compressed air at a pressure of 4.5 bars.
  • This jet of compressed air has the effect of overcoming the lines of force of the electrostatic field and deflecting the powder towards the throat of the matrix.
  • the air jet is also activated 8 seconds after the electrode arrays are energized, and for a period of 2 seconds. The actuation of the electrostatic powder system and the air supply system is then interrupted.
  • Such a process makes it possible to obtain a perfect distribution of the powder on the different surfaces of the matrix, the thickness of powder deposited being uniform and 0.25 mm ⁇ 0.1 mm.

Landscapes

  • Application Of Or Painting With Fluid Materials (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Paints Or Removers (AREA)
  • Glanulating (AREA)
EP90201486A 1989-06-16 1990-06-09 Verfahren zur elektrostatischen Pulverbeschichtung eines Gegenstandes mit pulverförmigen oder körnigen Partikeln und Vorrichtung zur Durchführung dieses Verfahrens Expired - Lifetime EP0403002B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90201486T ATE99996T1 (de) 1989-06-16 1990-06-09 Verfahren zur elektrostatischen pulverbeschichtung eines gegenstandes mit pulverfoermigen oder koernigen partikeln und vorrichtung zur durchfuehrung dieses verfahrens.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8908160 1989-06-16
FR8908160A FR2648369B1 (fr) 1989-06-16 1989-06-16 Procede de poudrage electrostatique en vue de revetir un objet de particules pulverulentes ou granuleuses, et dispositif pour la mise en oeuvre de ce procede

Publications (2)

Publication Number Publication Date
EP0403002A1 true EP0403002A1 (de) 1990-12-19
EP0403002B1 EP0403002B1 (de) 1994-01-12

Family

ID=9382914

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90201486A Expired - Lifetime EP0403002B1 (de) 1989-06-16 1990-06-09 Verfahren zur elektrostatischen Pulverbeschichtung eines Gegenstandes mit pulverförmigen oder körnigen Partikeln und Vorrichtung zur Durchführung dieses Verfahrens

Country Status (4)

Country Link
EP (1) EP0403002B1 (de)
AT (1) ATE99996T1 (de)
DE (1) DE69005911D1 (de)
FR (1) FR2648369B1 (de)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282520B (de) * 1962-08-04 1968-11-07 Eric Alton Dr Ing Vorrichtung zum elektrostatischen Beschichten von metallischen, insbesondere aus Draht hergestellten Werkstuecken mit pulverfoermigen Kunststoffen
DE1427641A1 (de) * 1962-11-30 1968-11-14 Siemens Elektrogeraete Gmbh Verfahren und Vorrichtung zum Beschichten von Werkstueckoberflaechen in einem Wirbelsinterbad
DE2036279A1 (de) * 1970-07-22 1972-01-27 Stutz, Erwin, 7075 Mutlangen Verfahren und Vorrichtung zum Abstoßen von Teilchen von einer Unterlage
DE2145039A1 (de) * 1971-09-09 1973-03-22 Ahlmann Aco Severin Verfahren und vorrichtung zum aufbringen von emailpuder auf zu emaillierende gegenstaende

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282520B (de) * 1962-08-04 1968-11-07 Eric Alton Dr Ing Vorrichtung zum elektrostatischen Beschichten von metallischen, insbesondere aus Draht hergestellten Werkstuecken mit pulverfoermigen Kunststoffen
DE1427641A1 (de) * 1962-11-30 1968-11-14 Siemens Elektrogeraete Gmbh Verfahren und Vorrichtung zum Beschichten von Werkstueckoberflaechen in einem Wirbelsinterbad
DE2036279A1 (de) * 1970-07-22 1972-01-27 Stutz, Erwin, 7075 Mutlangen Verfahren und Vorrichtung zum Abstoßen von Teilchen von einer Unterlage
DE2145039A1 (de) * 1971-09-09 1973-03-22 Ahlmann Aco Severin Verfahren und vorrichtung zum aufbringen von emailpuder auf zu emaillierende gegenstaende

Also Published As

Publication number Publication date
DE69005911D1 (de) 1994-02-24
EP0403002B1 (de) 1994-01-12
FR2648369B1 (fr) 1993-06-11
FR2648369A1 (fr) 1990-12-21
ATE99996T1 (de) 1994-01-15

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